Dear Scott
I`v sat through 12 presentations and 12 demonstrations on air tools in the
context of soil movement and yes I can confirm a barrier was always employed
and in some instances sheets laid out to collect the soil, personally I
thought it too obvious to mention.
It depends greatly on the type of soil and the conditions on the day. I have
seen it come out in great lumps replaced by hand, spade and rake. There have
been other extremes when the soil has broken down into a fine dust and been
carried away in the wind. The latter I associated with hard compacted
soil void of much moisture.
With regard to it being good for compaction, did I not say I do not think it
good for such a use. but great for radial trenching, vertical mulching
and general root exposure.
I have a 32 page training manual on the uses and applications including
radial trenching. No where does it suggest this is for reducing compaction,
instead it refers to radial or vertical trenching and the application of soil
amendments. To any one with experience of the tool, that too would
be obvious.
Earth augers or other methods for drilling a hole in the ground may well
be preferable, I regularly use an earth auger on installs to great affect.
To conclude I would say if you really need to shift soil at a rate of a cubic
meter a minute then consider it, personally for what I do it is overkill. I
get by with hand tools.
I doubt you require clarification on hand tool, as I`m sure
your familiar with those.
________________________________
From: Scott Cullen <dscottcul@xxxx.net>
To: UK Tree Care <uktc@xxxxxx.tree-care.info>
Sent: Tuesday, 27 March 2012, 11:58
Subject: Re: Air Spade/Lance/Pick
----- Original Message -----
From: BENJAMIN FUEST
To: UK Tree Care
Sent: Monday, March 26, 2012 3:13 PM
Subject: Re: Air Spade/Lance/Pick
BF For what its worth I took part in a series of workshops across America
and one of the topics covered was the air spade, I loved it. The
demonstrations were mainly on trenching for the lightning protection systems
but other applications were also discussed and demonstrated.
BF The matching of nozzle to lance and compressor output are important and
I recall an air speed approaching mach two was possible but there was not a
lot left after the event to put back in the trench. So a lot of infill had to
be provided from elsewhere.
SC Ben I suspect the excavated material remains in the general area. It
has to go somewhere. Often the work set up includes some sort of barrier
"downwind," so to speak, against which the material accumultaes. In a single
trench (say for a grounding conductor or some other utility) the imported
backfill material (assuming none of the original was collected and it's
decent new soil) isn't going to change overall conditions much. And a lot of
the apparently missing stuff is likely spread over the rest of the root
system.
BF Very very noisy and dirty stuff from granular to quite large rocks can
be thrown some distance. From observation I would not think good for de
compaction/fracturing of soil structure
SC I'm pretty sure it is not intended to fracture a soil profile. It's an
excavation tool. In terms of decompaction whether by radial trenching or
larger areas of root system, just fluffing it up is not of lasting benefit.
The fluffed up and re-placed soil because of its structure is likely to
recompact, There have been some experiments demonstrating that macroporosity
is better maintained by amending with compost. I imagine all new soil or
partially new soil mixed in could be effective as well.
BF but great for radial trenching, vertical mulching or general root
exposure,
SC Assuming vertical mulching is seen as effective, an airspade may or may
not be the most effective tool. Vertical use is called "potholing" and it
may be problematic to have loosened soil just accumulating in the bottom of
the whole, ultimately limiting the ability to go deeper. The best solution
is a vacume. That can be a separate unit (from an electric shop vac for
small volumes) to the giant truck mounted vacs used to clean storm drains.
Or a compressor powered vac as an accessory to the air spade but it requies a
much larger compressor. Assuming some loss of small roots is acceptable and
you're well away from larger roots, a soil auger or post hole digger can be
easier to set up and use.
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